The official Google+ pages of guest houses and hotels from around the world have had details "hijacked" by an unknown third party, leading to their official websites redirecting to an external web address.
The web addresses listed were altered to point to a third-party booking services, RoomsToBook.Info and RoomsToBook.Net.
The comprehensive and sprawling hack has led to accusations of an "inside job" at Google.
RoomsToBook.Info and RoomsToBook.Net have refused to comment when contacted by journalists.
However, the director of HotelsWhiz.com, Karim Mawani, issued the following statement to Danny Sullivan of Search Engine Land, who discovered the hijacks and reported them on his blog:
"We have recently seen this issue and have reported to Google webmaster already. If you have seen any links please forward it to me and I will submit the request. Our team is already in process of blocking list of certain domains and IP addresses from back-linking us. Thank you for pointing this out if you have any more external domains acting in above manner please report it to us."
Some compromised pages that were formerly in Google+ Local have now been entirely removed.
"My prediction is, this was an inside job with someone at Google," said Matthew Hoff of public relations company Merkle.
"Not to be a conspiracy theorist, but any and all modified URLs have to be okay'ed by a Maps moderator. No one is dumb enough to believe the official URL of a hotel lives on roomstobook.info... come on!"
Google has told the press that it is "aware of the issue and we are working to fix it". It has refused to comment on the possibility that an insider was responsible for the devastating breach.
This reported hack comes just two days after a Google maps moderator was suspended for erroneously approving the change of Berlin's Theodor-Heuss-Platz to its one-time name of "Adolf-Hitler-Platz."